Volume, Freshwater, and Heat Fluxes Through Davis Strait, 2004–05*

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Volume, Freshwater, and Heat Fluxes through Davis Strait, 2004–05*

B. CURRY AND C. M. LEE Applied Physics Laboratory, University of Washington, Seattle, Washington

B. PETRIE Ocean Sciences Division, Bedford Institute of Oceanography, Dartmouth, Nova Scotia, Canada

(Manuscript received 29 July 2010, in ﬁnal form 25 October 2010)

ABSTRACT

Davis Strait volume [22.3 6 0.7 Sv (1 Sv [ 106 m3 s21); negative sign indicates southward transport], freshwater (2116 6 41 mSv), and heat (20 6 9 TW) fluxes estimated from objectively mapped 2004–05 moored array data do not differ significantly from values based on a 1987–90 array but are distributed dif- ferently across the strait. The 2004–05 array provided the first year-long measurements in the upper 100 m and over the shelves. The upper 100 m accounts for 39% (20.9 Sv) of the net volume and 59% (269 mSv) of the net freshwater fluxes. Shelf contributions are small: 0.4 Sv (volume), 15 mSv (freshwater), and 3 TW (heat) from the West Greenland shelf and 20.1 Sv, 27 mSv, and 1 TW from the Baffin Island shelf. Contempo- raneous measurements of the Baffin Bay inflows and outflows indicate that volume and freshwater budgets balance to within 26% and 4%, respectively, of the net Davis Strait outflow. Davis Strait volume and freshwater fluxes nearly equal those from Fram Strait, indicating that both are significant Arctic freshwater pathways.

1. Introduction affect western North Atlantic continental shelf ecosystems (Greene et al. 2008). Arctic waters flow into the North Atlantic through Davis Strait captures the CAA outflow after modifica- the Canadian Arctic Archipelago (CAA) and Fram tion during its transit through Baffin Bay to the Labrador Strait (Aagaard and Carmack 1989). Recent changes in Sea (Fig. 1a). Arctic Ocean waters, entering northern the Arctic including increased air temperatures (e.g., Baffin Bay through Nares Strait and Jones and Lancaster Overland et al. 2008), enhanced sea ice loss (e.g., Wang Sounds, flow southward along Baffin Island through Davis and Overland 2009), increased Canadian river discharge Strait as the broad, surface-intensified Baffin Island Cur- (De´ry et al. 2009), and ice-free CAA channels (Canadian rent (BIC; Tang et al. 2004; Cuny et al. 2005). Northward Ice Service; available online at http://ice-glaces.ec.gc.ca/) flow on the eastern side of Davis Strait consists of the fresh suggest potentially large changes in volume, freshwater, West Greenland Current (WGC) of Arctic origin on the and heat transports between the Arctic and North Atlantic shelf and warm, salty West Greenland Slope Current Oceans. Variability in freshwater export through Davis (WGSC) of North Atlantic origin on the slope. These Strait could impact North Atlantic deep convection (e.g., inflowing waters, modified during their cyclonic circula- Va˚ge et al. 2009), alter the strength of the Atlantic me- tion in Baffin Bay, join the BIC and exit western Davis ridional overturning circulation (Holland et al. 2001), and Strait at depths typically .400 m. The net Baffin Bay outflow combines CAA flows, river runoff, sea ice, and * Supplemental information related to this paper is available at the inputs from Greenland and the North Atlantic. The Journals Online Web site: http://dx.doi.org/10.1175/2010JPO4536.s1. smaller Fury and Hecla Strait component [0.1 Sv (1 Sv [ 106 m3 s21 5 31 536 km3 yr21) volume and 38 mSv Corresponding author address: Beth Curry, Applied Physics freshwater] of the CAA outflow bypasses Baffin Bay Laboratory, 1013 NE 40th St., Seattle, WA 98105. and enters the Labrador Sea through Hudson Strait E-mail: [email protected] (Straneo and Saucier 2008).

DOI: 10.1175/2010JPO4536.1

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moorings (4 per shelf and 6 central moorings; Figs. 1b,c) north of the sill (640 m) at a maximum depth of 1040 m. Instrumentation measured velocity, temperature, and conductivity at 30 min and hourly intervals. On the Baffin Is- land shelf, a prototype iceberg-resistant mooring (IceCAT), consisting of a float and SBE37 MicroCAT inductively coupled to a bottom-mounted datalogger measured temperature and conductivity at 5-min intervals. Currents were resolved parallel and orthogonal to the array line (77.38); tidal variability was removed with a 34-h low-pass Butterworth filter and subsampled to obtain daily values; and missing data were filled by interpolation and extrapolation using archived data to produce full-depth temperature (T) and salinity (S;BIO;T and S data are available online at http://www.mar.dfo-mpo.gc.ca/science/ ocean/) and along-strait velocity (V) profiles at each mooring (see appendix A of online supplement). b. Objective mapping Objective analysis (OA; Bretherton et al. 1976) was used to construct daily variable (5observed value 2 mean value) maps of V, T,andS fields using a Gaussian covariance function. Correlations calculated from hydrographic sections and mooring time series yielded horizontal decorrelation length scales of 20 (V)and 40 km (T and S). Slowly varying daily-mean fields were created using further low-passed data (10-day cutoff to reduce tidal and meteorological variability) and spatially averaged into domains defined by depth (0–150, 200–250, and 500 m) and location (e.g., the shelves and WGSC– BIC frontal zone). The mean and variable fields were mapped onto a regular, two-dimensional grid with 4-m cells at depths ,150 m and 10-m cells at depths .150 m at a horizontal resolution of 5 km (see appendix B of online supplement). c. Flux calculations Daily volume, freshwater, and heat fluxes were averaged to compute monthly and annual fluxes. The refer- FIG. 1. (a) General circulation in Baffin Bay and Davis Strait ence salinity (34.8, mean Arctic Ocean salinity; Aagaard (white arrows) noting the BIC, WGC, WGSC, and moored array (red and Carmack 1989), sea ice salinity (5), and temperature line). (b) Zoom panel of Davis Strait and 2004–05 (red squares) and (08C) were chosen to maintain consistency with Cuny 1987–90 (black squares) mooring sites. (c) Moored array instruments, depths, and locations. Blue crosses indicate SBE37 MicroCAT con- et al. (2005). Mooring deployment and recovery provided ductivity, temperature, and pressure recorders; green dots represent ,10 days of data in September, insufficient to compute RDI ADCPs; black dots denote Aanderaa RCM8 velocity, con- reliable flux estimates for that month. Monthly fluxes ductivity, and temperature recorders; and red dots denote Aanderaa for September 2005 were estimated as the average of RCM8 velocity and temperature recorders. Inset image shows a October 2004 and August 2005 values. close-up of the Baffin Island shelf instruments. d. Uncertainties 2. Data and methods Flux uncertainties were estimated as the sum of OA a. Data random error, standard error of the mean calculated A long-term monitoring program in Davis Strait began using the Student’s t distribution with 95% confidence in September 2004. The 2004–05 program included 14 limits, and maximum range of flux estimates obtained

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FIG. 2. Objectively analyzed monthly mean (a) along-strait velocity, (b) salinity, and (c) temperature. Gray lines indicate moorings, white dots indicate instrument locations for each property, and the pink bars indicate areas along the moored array that are covered by sea ice 60% of the month. The 34.8 salinity contour (dashed black line) and the 27 kg m23 isopycnal (black line) are noted in (b). Mean salinities $ 34.8 were seen only in October. The boundaries of the four dominant water masses (see Fig. 3 for u–S characteristics) are shown for October in (c).

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FIG. 3. Davis Strait water masses defined using potential temperature (u) and S: AW (red ellipse; u # 18C; S # 33.7) present in the western strait at depths ,300 m, WGIW (blue ellipse; u . 28C; S . 34.1) along the WG slope, WGSW (green ellipse; u , 78C; S , 34.1), and TrW (magenta ellipse; u # 28C; S . 33.7) usually at depths .300 m. Water masses are illustrated using September 2004 (black squares) and September 2005 (gray circles) hydrographic data along the mooring line. using different approaches to compute the mean field. Baffin Island (Figs. 2b,c). Salinity increased ;0.4 from Additional uncertainties associated with the ice flux and December to March in the upper 200 m with local ice estimation of the shelf and 0–100-m salinities were added formation (;1.25 m) accounting for only ;0.1 of the in- to the freshwater flux uncertainty estimate. Sensitivity crease, with the remaining due to salt advection. The tests were performed to estimate flux variability asso- strong BIC–WGSC frontal zone, separating Arctic Water ciated with differences in mean field and sea ice flux. (AW) and transitional water (TrW) from West Green- land Irminger Water (WGIW), is evident over the slope. Maximum temperatures and salinities of the WGIW 3. Results and discussion occurred in autumn, decreased until April and remained a. Current and water mass structure nearly constant until August, consistent with advection from the south (M. Stein 2009, personal communication). Circulation during 2004–05 was dominated by north- Recirculated WGIW influenced the temperature of TrW, ward flow on the West Greenland (WG) shelf and slope but their temperature variations were not well correlated, and southward flow over the remaining strait with possibly due to variations in recirculation and mixing time weaker currents below 200 m (Fig. 2a). The surface- scales in Baffin Bay. The WGSW temperature had an intensified (upper 200 m) southward flow extended east- annual cycle of ;68C with a late summer maximum and ward ;150 km from Baffin Island with a bimodal structure March minimum. Salinity variations on the WGSW (au- featuring strong flows over the slope, weaker currents tumn minimum, May maximum, and typically freshest at approximately 100 km offshore, and maximum veloci- the coast) reflect melting Arctic sea ice advected from ties at the BIC–WGSC front. The narrow (;50 km) Fram Strait, local and advected runoff, and interactions WGSC had an average velocity magnitude 7 times with WGIW. Ice was present from November 2004 to July greater than the WGC. Opposing currents in the BIC– 2005 with peak coverage in February. WGSC front were strongest in autumn and winter and present in all months but April. A weak northward b. Annual and monthly fluxes flow over the Baffin slope in December and January was also noted by Tang et al. (2004) and Cuny et al. Mean volume, freshwater (including sea ice), and (2005). heat fluxes through Davis Strait, from October 2004 to Following the definitions of Tang et al. (2004), four September 2005, were 22.3 6 0.7 Sv, 2116 6 41 mSv, water masses are identified in Davis Strait and defined in and 20 6 9 TW, respectively. Because autumn CTD data Fig. 3. Arctic Water dominated the upper layers to depths suggest that waters below the sill did not cross the strait, approaching 200 m and extending to ;200 km from flux calculations were extended only to 640 m. Transport

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FIG. 4. Monthly-mean fluxes, including uncertainties, for (a) volume, (b) liquid freshwater (reference 34.8), and (c) heat (reference 08C). Daily fluxes are shown in gray and annual mean fluxes, including uncertainties, are noted in the bottom right of each panel. The annual freshwater flux estimate includes the contribution from sea ice (211 mSv). All fluxes are estimated from the surface to the sill depth (640 m). from 0 to 100 m was 39% (20.9 Sv) of the net volume The September linearly interpolated volume and fresh- and 59% (269 mSv) of the net freshwater fluxes. Shelf water fluxes, 21.7 Sv and 299 mSv, agreed well with the contributions were small: for WG, 0.4 Sv of volume, geostrophic estimates from the hydrographic sections for 15 mSv of liquid freshwater, and 3 TW of heat; the Baffin 2004 (21.9 Sv and 296 mSv) and 2005 (22.6 Sv and Island shelf accounted for 20.1 Sv, 27mSv,and1TW. 2107 mSv), particularly for freshwater. The geostrophic The heat flux estimates must be viewed with caution transports were based on a ;1-day transect of the strait because the net volume flux is not zero (Schauer et al. and neglect barotropic contributions, particularly large 2008). for the northward WGSC, which could account for the Net monthly volume and freshwater fluxes were south- larger difference in volume transport. ward year round with weak peaks in December–January Sea ice contributes significantly only to the freshwater and June (Fig. 4). Though not statistically significant, the flux. Kwok (2007) estimated that 360 3 103 km2 of sea ice peaks suggest transport may have been driven by ad- with an average thickness of 1–1.5 m was exported be- vection (December–January) from the Arctic Ocean via tween November 2004 and May 2005. Assuming a thick- the CAA and local (June) forcing related to the spring– ness of 1.25 m, this implies 450 km3 of sea ice export, summer Baffin Bay ice melt. A reasonable advection which, when combined with the estimate from Jordan speed of 0.08–0.12 m s21 is required for the broad June– and Neu (1982) of 17 km3 for June and July, yields August transport peak in Lancaster Sound (Prinsenberg 467 km3 yr21 or 11 mSv of freshwater export through et al. 2009) to have triggered the December–January Davis Strait. transport peak at Davis Strait. Heat flux was strongest c. Water mass fluxes between October and December because of increased southward transport of cold BIC water and northward Particular water masses dominate the heat and freshwa- transport of warm WGSC water: it was nearly constant ter fluxes. The annual negative liquid volume flux (24.2 Sv) between January and August. consists of 50% (22.1 Sv) AW and 40% (21.7 Sv) TrW.

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TABLE 1. Bafﬁn Bay volume and freshwater (referenced to 34.8) budgets.

Volume transport (Sv) Freshwater transport (mSv) Baffin Bay passages Inflow Outflow Inflow Outflow Nares Strait (2003–06)a 0.72 6 0.11 28 6 3 Lancaster Sound (1998–2006)b 0.7 6 0.2 48 6 15 Jones Sound (1998–2002)c 0.3 6 0.1 12 6 4 CAA Ice (1996–2007)d ,0.1 5.7 6 1 Greenland Ice Sheet (1995–2007)e ,0.1 7.2 6 1 P-E (1961–2001)f ,0.1 7.0 6 4 Baffin Island Runoff (1971–2000)g ,0.1 2.8 6 1 Davis Strait (2004–05) 22.3 6 0.7 2116 6 41

Total 1.7 6 0.2 22.3 6 0.7 111 6 16 2116 6 41 Difference 20.6 25 a From Mu¨ nchow and Melling (2008) and Rabe et al. (2010). b From Prinsenberg et al. (2009). c From Melling et al. (2008). d From Agnew et al. (2008) and Kwok (2005). e From Mernild et al. (2009). f From Canadian Climate and Data Information Archive (available online at http://www.climate.weatherofﬁce.ec.gc.ca), Jensen and Rasch (2008), National Climate Data Center (available online at http://www.ncdc.noaa.gov/oa/ncdc.html), Ka˚llberg et al. (2005), and Danish Meteorological Institute (available online at http://www.dmi.dk/dmi/index/gronland/klimanormaler-gl.htm). g From Canadian Climate and Data Information Archive (available online at http://www.climate.weatherofﬁce.ec.gc.ca) and Water Survey of Canada (available online at geogratis.cgdi.gc.ca/geogratis/en/index.html).

The fresher AW makes up 72% (2103 mSv) of the annual (22.6 6 1Sv,292 6 34 mSv, and 18 6 17 TW; Cuny negative liquid freshwater flux (2143 mSv), whereas TrW et al. 2005), but the WG shelf contributions differ sub- contributes only 23% (233 mSv). The annual positive stantially. The 2004–05 volume, freshwater, and heat flux heat flux (130 TW) shows 37% (111 TW) from AW, estimates for the WG shelf (0.4 Sv, 15 mSv, and 3 TW) 37% (111 TW) from WGIW, and 10% (13TW)from are less than half the 1987–90 estimates (0.8 Sv, 38 mSv, WGSW. and 7 TW). Neglecting the fluxes over the WG shelf where Cuny et al. (2005) had no measurements, net d. Comparisons to previous studies southward volume and liquid freshwater fluxes have decreased between 1987–90 (23.4 Sv and 2130 mSv) and These results extend the Davis Strait flux estimates 2004–05 (22.7 Sv and 2120 mSv), not a statistically sig- beyond 1987–90 (Ross 1992) and are more robust. The nificant margin but nonetheless intriguing and contrary to 1987–90 estimates, based on six central strait moorings, expectations. The solid (ice) component of freshwater flux lacked measurements shallower than 150 m and over both between 2004 and 2005 (211 mSv) nearly matches the shelves, where the 2004–05 results indicate that 55% estimate from 1987 to 1990 (212.9 mSv). (73%) of the volume (liquid freshwater) transport occurs. Three studies using the 1987–90 data adopted different e. Baffin Bay budgets approaches for extrapolating across the upper 150 m and either made highly uncertain estimates of shelf contribu- Contemporaneous measurements across the primary tions (Cuny et al. 2005) or confined their analyses to the pathways of Baffin Bay, combined with estimates of ice central strait (Loder et al. 1998; Tang et al. 2004). Dif- contributions, precipitation less evaporation (P-E), and ferences in upper-layer extrapolation methods pro- historical data from Jones Sound, allow assessment duced volume fluxes ranging from 23.3 to 22.6 (61.2) of Baffin Bay volume and freshwater budgets (Table 1; Sv, liquid freshwater fluxes ranging from 2120 to 292 see appendix C of the online supplement for details). (634) mSv, and a heat flux (only Cuny et al. 2005) of Budgets close to within 0.6 Sv for volume and 5 mSv for 18 6 17 TW. The freshwater transport from ice ranged freshwater: both are within the uncertainties of the esti- from 221.3 mSv (873 km3 yr21; Tang et al. 2004) to mates. These imbalances represent 26% and 4% of the 212.9 mSv (528 km3 yr21; Cuny et al. 2005). net annual volume and freshwater transports through The 2004–05 volume, liquid freshwater, and heat flux Davis Strait and provide a rough gauge of the array’s estimates (22.3 6 0.7 Sv, 2105 6 41 mSv, and 20 6 9TW) ability to monitor the fluxes. The larger volume flux im- are within the uncertainties of the 1987–90 estimates balance may reflect decreased resolution below 200 m in

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Davis Strait (a larger fraction of the volume, relative to Agnew,T.,A.Lambe,andD.Long,2008:Estimatingseaiceareaflux freshwater, flux is in the deeper layer) or interannual across the Canadian Arctic Archipelago using enhanced AMSR-E. variability. J. Geophys. Res., 113, C10011, doi:10.1029/2007JC004582. Bretherton, F. P., R. E. Davis, and C. B. Fandry, 1976: A technique f. Comparison to Fram Strait for objective analysis and design of oceanographic experiments applied to MODE-73. Deep-Sea Res., 23, 559–582, doi:10.1016/ Net volume and freshwater transports through Davis 0011-7471(76)90001-2. Strait are similar in magnitude to those estimated for Fram Cuny, J., P. Rhines, and R. Kwok, 2005: Davis Strait volume, fresh- Strait, the other major pathway connecting the Arctic and water and heat fluxes. Deep-Sea Res. I, 52, 519–542, doi:10.1016/ j.dsr.2004.10.006. North Atlantic. Davis Strait net volume and freshwater De´ry, S. J., M. A. Hernańdez-Hernrı´quez, J. E. Buford, and fluxes are within the uncertainty of the Fram Strait esti- E. F. Wood, 2009: Observational evidence of an intensifying mates [22.3 6 4.3 Sv (Schauer et al. 2008; Rudels et al. hydrological cycle in northern Canada. Geophys. Res. Lett., 36, 2008) and 2119 6 40 mSv (Rudels et al. 2008; Kwok et al. L13402, doi:10.1029/2009GL038852. 2004); see appendix D of online supplement]. Estimates Greene, C. H., A. J. Pershing, T. M. Cronin, and N. Ceci, 2008: Arctic climate change and its impacts on the ecology of the of volume and freshwater outflows for the Barents Sea North Atlantic. Ecology, 89, S24–S38, doi:10.1890/07-0550.1. (Skagseth et al. 2008; Ingvaldsen et al. 2004; Aagaard and Holland, M., C. Bitz, M. Eby, and A. Weaver, 2001: The role of ice– Carmack1989)andHudsonStrait(StraneoandSaucier ocean interactions in the variability of the North Atlantic 2008) indicate that Davis and Fram Straits combined ac- thermohaline circulation. J. Climate, 14, 656–675. count for 98% of the total volume and 84% of the total Ingvaldsen, R., L. Asplin, and H. Loeng, 2004: The seasonal cycle in the Atlantic transport to the Barents Sea during the years 1997–2001. freshwater Arctic outflows. Cont. Shelf Res., 24, 1015–1032, doi:10.1016/j.csr.2004.02.011. Jensen, L., and M. Rasch, 2008: Nuuk ecological research opera- 4. Conclusions tions. 2007, Danish Polar Centre, Danish Agency for Science, Technology and Innovation First Annual Rep., 112 pp. Davis Strait, along with Fram Strait, represents a critical Jordan, F., and H. J. A. Neu, 1982: Ice drift in southern Baffin Bay component of Arctic volume and freshwater budgets and and Davis Strait. Atmos.–Ocean, 20, 268–275. an important input of freshwater for the subpolar North Ka˚llberg, P., P. Berrisford, B. Hoskins, A. Simmons, S. Uppala, Atlantic. The 2004–05 fluxes are statistically similar to S. Lamy-The´paut, and R. Hine, 2005: ERA-40 atlas. ECMWF ERA-40 Project Rep. 19, 191 pp. those calculated for 1987–90 , though comparisons suggest Kwok, R., 2005: Variability of Nares Strait ice flux. Geophys. Res. a decrease of the volume transport for the central strait. Lett., 32, L24502, doi:10.1029/2005GL024768. Varying methodologies, observational coverage, and re- ——, 2007: Baffin Bay ice drift and export: 2002–2007. Geophys. cord length along with interannual variability create Res. Lett., 34, L19501, doi:10.1029/2007GL031204. a somewhat disparate comparison, suggesting a reanalysis ——, G. F. Cunningham, and S. S. Pang, 2004: Fram Strait sea ice outflow. J. Geophys. Res., 109, C01009, doi:10.1029/2003JC001785. using common methodologies. Larger differences might Loder, J., B. Petrie, and G. Gawarkiewicz, 1998: The coastal ocean have been expected given recent changes seen in the off northeastern North America: A large-scale view. The Sea, A. Arctic and CAA. Continued measurements are needed Robinson and K. Brink, Eds., The Global Coastal Ocean: Re- to monitor and understand any variability of the CAA gional Studies and Syntheses, Vol. 11, Harvard University Press, outflow in response to Arctic change. 105–133. Melling, H., and Coauthors, 2008: Fresh-water fluxes via Pacific Acknowledgments. This study is part of U.S. National and Arctic outflows across the Canadian polar shelf. Arctic- Subarctic Ocean Fluxes: Defining the Role of the Northern Seas Science Foundation Freshwater Initiative (2004–2007) and in Climate, R. Dickson, J. Meincke, and P. Rhines, Eds., the International Polar Year and Arctic Observing Net- Springer Verlag, 193–247. work (2007–2010) programs under Grants OPP0230381 Mernild, S. H., G. E. Liston, C. A. Hiemstra, K. Steffen, E. Hanna, and OPP0632231. Additional support was provided by and J. H. Christensen, 2009: Greenland ice sheet surface mass- the Department of Fisheries and Oceans, Canada. Knut balance modelling and freshwater flux for 2007, and in a 1995– 2007 perspective. Hydrol. Processes, 23, 2470–2484, doi:10.1002/ Aagaard, Je´roˆme Cuny, Humfrey Melling, Peter Rhines, hyp.7354. and Charles Tang contributed to the array design. Jason Mu¨ nchow, A., and H. Melling, 2008: Ocean current observations Gobat, Eric Boget, James Johnson, Keith VanThiel, from Nares Strait to the west of Greenland: Interannual to Murray Scotney, Victor Soukhovstev, and James Abriel tidal variability and forcing. J. Mar. Res., 66, 801–833. were essential to the measurement program. Overland, J., M. Wang, and S. Salo, 2008: The recent Arctic warm period. Tellus, 60, 589–597. Prinsenberg, S., J. Hamilton, I. Peterson, and R. Pettipas, 2009: REFERENCES Observing and interpreting the seasonal variability of the oceanographic fluxes passing through Lancaster Sound of the Aagaard, K., and E. Carmack, 1989: The role of sea ice and other Canadian Arctic Archipelago. Influence of Climate Change on fresh water in the Arctic circulation. J. Geophys. Res., 94 the Changing Arctic and Sub-Arctic Conditions, J. C. J. Nihoul (C10), 14 485–14 498. and A. Kostianoy, Eds., Springer, 125–143.

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Rabe, B., A. Mu¨nchow, H. L. Johnson, and H. Melling, 2010: Nares to the Arctic Ocean via the Norwegian and Barents Seas. Strait hydrography and salinity field from a 3-year moored array. Arctic-Subarctic Ocean Fluxes: Defining the Role of the North- J. Geophys. Res., 115, C07010, doi:10.1029/2009JC005966. ern Seas in Climate, R. Dickson, J. Meincke, and P. Rhines, Eds., Ross, C., 1992: Moored current meter measurements across the Davis Springer Verlag, 45–64. Strait. NAFO Research Document Tech. Rep. 92/70, 8 pp. Straneo, F., and F. Saucier, 2008: The Arctic-subarctic exchange Rudels, B., M. Marnela, and P. Eriksson, 2008: Constraints on es- through Hudson Strait. Arctic-Subarctic Ocean Fluxes: De- timating mass, heat and freshwater transports in the Arctic fining the Role of the Northern Seas in Climate, R. Dickson, Ocean: An exercise. Arctic-Subarctic Ocean Fluxes: Defining J. Meincke, and P. Rhines, Eds., Springer Verlag, 249–261. the Role of the Northern Seas in Climate, R. Dickson, J. Meincke, Tang, C. C. L., C. K. Ross, T. Yao, B. Petrie, B. M. DeTracey, and and P. Rhines, Eds., Springer Verlag, 315–341. E. Dunlap, 2004: The circulation, water masses and sea-ice Schauer, U., A. Beszczynska-Mo¨ ller, W. Walczowski, E. Fahrbach, of Baffin Bay. Prog. Oceanogr., 63, 183–228, doi:10.1016/ J. Piechura, and E. Hansen, 2008: Variation of measured heat j.pocean.2004.09.005. flow through the Fram Strait between 1997 and 2006. Arctic- Va˚ge, K., and Coauthors, 2009: Surprising return of deep convec- Subarctic Ocean Fluxes: Defining the Role of the Northern Seas tion to the subpolar North Atlantic Ocean in winter 2007– in Climate, R. Dickson, J. Meincke, and P. Rhines, Eds., 2008. Nat. Geosci., 2, 67–72, doi:10.1038/ngeo382. Springer Verlag, 65–85. Wang, M., and J. E. Overland, 2009: A sea ice free summer Arctic Skagseth, O., T. Furevik, R. Ingvaldsen, H. Loeng, K. Mork, within 30 years? Geophys. Res. Lett., 36, L07502, doi:10.1029/ K. Orvik, and V. Ozhigin, 2008: Volume and heat transports 2009GL037820.

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